The present invention is directed to an environmentally-safe, non-toxic photographic developer composition.
Photographic developer compositions are well-known in the art. The processing of silver halide photographic materials is performed by a multiple step sequence consisting of development, stopping, fixing and washing steps.
The development step is conventionally undertaken with an aqueous alkaline developer composition containing a developer such as hydroquinone and/or other well-known developing agents.
More specifically, the exposure of a silver halide emulsion to radiation to which the emulsion is sensitized produces a latent image in the silver halide grains of the emulsion. The latent image is developed by immersion of the exposed emulsion in an aqueous developing solution which contains a reducing agent (or developer). The hydroquinone or other suitable developer material serves as a strong silver reducing agent to reduce the exposed silver halide grains to yield the developed photographic image.
Exemplary hydroquinone-based developer compositions are disclosed in, for example, U.S. Pat. Nos. 2,893,865; 3,733,199; 3,865,591; 4,046,571; 4,205,124; 4,756,990; and 4,816,384. Normally, these compositions contain relatively high levels of sulfite-based components.
It is also important to maintain the pH of the developer composition within strict alkaline ranges to ensure satisfactory operation of the composition. As a result, caustic alkalis (caustic soda or caustic potash) are frequently employed in the developer composition.
While hydroquinone-based developer compositions have been employed with success for many years, more recently the use of such compositions has met with some doubt due to the toxicity and environmental hazards posed by the use of the hydroquinone, sulfite and caustic alkali components. That is, due to the toxic nature of various of the components employed in conventional developer compositions, and the resultant high pH, it is necessary to meet various guidelines and regulations promulgated to protect either the health of those who are exposed to such compositions or to protect the environment into which such compositions are disposed. As two of the least desirable of the components generally present in conventional developer compositions are hydroquinone and related materials and caustic alkalis, it would thus be desirable to discover acceptable substitutes therefore which are less toxic by nature.